Answers to the examples are:
1.) 2H2(g) + O2(g) ----> 2H2O(g) A synthesis (or combination) reaction.

2.) 2Ag2O(cr) ----> 4Ag(cr) + O2(g) A decomposition reaction.

3.) H2SO4(aq) +2NaOH(aq) ----> Na2SO4(aq) + 2H2O(l) A double-displacement reaction.

4.) CH4(g) + 2O2(g) ----> 2H2O(g) + CO2(g) A combustion reaction.